Which of the following is the correct chemical formula for the ionic compound rubidium cyanide?

• A. RbCN
• B. Rb2CN
• C. Rb(CN)2
• D. RbCNO

Answer: (A)

Verified step by step guidance

1. Identify the ions involved in the compound: rubidium (Rb) is a Group 1 metal that forms a +1 cation (Rb\^{+}), and the cyanide ion (CN\^{-}) is a polyatomic ion with a -1 charge.
2. Recall that ionic compounds are electrically neutral, so the total positive charge must balance the total negative charge.
3. Since rubidium has a +1 charge and cyanide has a -1 charge, they combine in a 1:1 ratio to balance the charges.
4. Write the formula by placing the cation first followed by the anion without any subscripts because the charges are already balanced: RbCN.
5. Verify that the formula represents a neutral compound by confirming the sum of charges: (+1) + (-1) = 0, which means the formula RbCN is correct.